Heterogeneous plasmonic photocatalyst of p-orbital metal, preparation method of heterogeneous plasmonic photocatalyst and method for catalyzing activation and conversion of saturated alkane into acetic acid by heterogeneous plasmonic photocatalyst

Abstract

The invention provides a p-orbital metal heterogeneous plasmonic photocatalyst, a preparation method and a method for catalyzing activation and conversion of saturated alkane into acetic acid by using the p-orbital metal heterogeneous plasmonic photocatalyst, and belongs to the technical field of heterogeneous plasmonic photocatalyst synthesis and photocatalytic organic synthesis. The method has the advantages of mild reaction conditions, high efficiency, high substrate yield and good selectivity. The method has important scientific significance and application value for promoting plasmon photocatalysis C (sp3)-H activation conversion, recycling of gaseous saturated alkane and carbon neutralization.

Description

Technical Field

[0001] The invention belongs to the technical field of heterogeneous plasmon photocatalyst synthesis and photocatalytic organic synthesis, and relates to a heterogeneous plasmon photocatalyst of p-orbital metal, a preparation method and a method for catalyzing the activation and conversion of saturated alkanes into acetic acid. Background Art

[0002] With the rapid development of economy and society, the consumption of traditional fossil fuels (such as oil, coal, natural gas, etc.) is increasing, making non-renewable resources on the verge of exhaustion; in addition, the combustion of fossil fuels will release a large amount of harmful substances, which will endanger human health and cause a series of environmental problems, such as greenhouse effect, air and water pollution. Therefore, carbon emissions and energy crisis have become two major problems for the development and progress of the world today. In order to achieve sustainable development and solve energy and environmental problems, the development of efficient, clean and low-cost methane activation and conversion technology has become a global research hotspot. Since the greenhouse effect caused by methane gas is more than 20 times that of the same amount of CO2, the use of abundant solar energy in nature to drive methane conversion will meet the requirements of carbon-based green energy and dual carbon goals at the same time, and is one of the most anticipated of various new unconventional strategies.

[0003] Carbon-hydrogen bond activation is a hot field that has developed rapidly in recent years. 3 )―H direct functionalization reaction of carbon-hydrogen bonds is known as the "holy grail of chemistry" due to its many outstanding advantages and great challenges, and has attracted the attention of more and more scientists. Using natural gas to replace oil to produce liquid fuels and basic chemicals has always been the focus of research and development in the scientific and industrial communities. Methane is the main component of natural gas and has tetrahedral symmetry. Saturated C(sp 3 )―H bond energy is as high as 435 kJ.mol -1 , is the most stable and cheapest organic small molecule in nature. The selective activation and directional conversion of methane has always been a world-class problem. So far, the conversion and utilization of natural gas has basically remained in the traditional high-temperature method, which not only requires large investment, high energy consumption, and low carbon utilization rate, but also releases a large amount of carbon dioxide while obtaining the product, which has a great impact on the ecological environment. Achieving efficient anaerobic activation and conversion of methane without the participation of oxidants and at room temperature is a major challenge in the field of catalysis and green energy.

[0004] Photoredox organic synthesis, as a cutting-edge direction in the field of photocatalysis, has attracted widespread attention. So far, this field has relied on the use of a limited range of precious metal-based chromophores or artificial organic dyes, and transition metal complex chromophores also have problems such as difficulty in recycling in homogeneous catalysis, low utilization rate, and high cost. Plasmonic photocatalysts based on the surface plasmon resonance effect of nanometals, as a new type of heterogeneous catalyst responsive to visible light, show great application potential in the conversion of solar energy into chemical energy. p-orbital metals are loaded on carbon material carriers to promote the transfer of photogenerated plasmon hot electrons and holes, achieve efficient separation of carriers, and improve the efficiency of plasmon catalysis. Transition metals and precious metals are usually used in photocatalytic redox organic reactions, as well as carbon-hydrogen activation conversion. Based on p-orbital metal heterogeneous plasmon photocatalysts, in the C(sp 3 )―H activation conversion has not been applied so far. Therefore, it is necessary to prepare, screen, and optimize high-performance p-orbital metal heterogeneous plasmon photocatalysts and apply them to the C(sp 3 )-H activation and conversion will be a major breakthrough in the field of plasmon catalysis for the activation and conversion of saturated alkanes such as methane. Summary of the invention

[0005] The present invention provides a preparation method of a heterogeneous plasmon photocatalyst based on p-orbital metal and a method for catalyzing the activation and conversion of small molecular saturated light alkanes of methane, ethane, propane and butane into acetic acid. To this end, the present invention provides a preparation method of a heterogeneous plasmon photocatalyst based on p-orbital metal, the method comprising: dispersing a p-orbital metal salt compound in a protic solvent, adding a carbon source, reacting at 120-300°C (for example, 120°C, 130°C, 150°C, 170°C, 180°C, 200°C, 220°C, 240°C, 260°C, 280°C or 300°C) for 4-36 h (for example, 4h, 8h, 16h, 26h or 36h), and calcining in an inert gas atmosphere (for example, argon or nitrogen) to obtain a preliminary product.

[0006] Preferably, the p-orbital metal compound can be one, two, three, four, five or six of the compounds of Sn, Sb, In, Pb, Bi, and Ga, including metal halides, nitric acid compounds, oxides, etc. (such as the p-orbital metal compound is tin tetrachloride, bismuth trichloride and / or antimony trichloride, etc.), and the p-orbital metal compound can be used at a concentration of 0.01-1.0 mmol / mL (for example, 0.01 mmol / mL, 0.05 mmol / mL, 0.1 mmol / mL, 0.2 mmol / mL, 0.3 mmol / mL, 0.4 mmol / mL, 0.5 mmol / mL, 0.6 mmol / mL, 0.7 mmol / mL, 0.8 mmol / mL, 0.9 mmol / mL or 1 mmol / mL); the carbon source can be one or more of glucose, cellulose, starch, etc., and the molar concentration of the carbon source can be 0.01-1.0 mmol / mL (for example, 0.01 mmol / mL, 0.05 mmol / mL, 0.1 mmol / mL, 0.2 mmol / mL, 0.3 mmol / mL, 0.4 mmol / mL, 0.5 mmol / mL, 0.6 mmol / mL, 0.7 mmol / mL, 0.8 mmol / mL, 0.9 mmol / mL or 1 mmol / mL) based on the volume of the protic solvent.

[0007] The preliminary product is separated by centrifugation, washed with ethanol and then vacuum dried. The drying temperature can be 50-80°C and the drying time can be 8-24 h to obtain a hydrothermal product.

[0008] Furthermore, the protic solvent is one or more of water, methanol, ethanol and ethylene glycol.

[0009] The above product is calcined under an inert atmosphere, the calcination temperature can be 650-950°C (for example, the calcination temperature can be 650°C, 700°C, 750°C, 800°C, 850°C, 900°C or 950°C), and the calcination time can be 2-6 h (for example, 2h, 3h, 4h, 5h or 6h) to obtain the target catalyst.

[0010] The catalyst can be applied to the C(sp 3 )-H activation conversion, completing the reaction of formula 1:

[0011] (Formula 1)

[0012] In particular, the aliphatic alkanes in Formula 1 are mainly small molecular saturated alkanes such as methane, ethane, propane and butane; the oxidant used is an aqueous solution of hydrogen peroxide, and its amount can be 1-30 wt% (e.g., 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20wt%, 25 wt% or 30 wt%).

[0013] Preferably, the molar concentration of the photocatalyst can be 0.05-2.0 mg / mL (e.g., 0.5 mg / mL, 1 mg / mL, 1.5 mg / mL or 2 mg / mL); the amount of gaseous alkanes such as methane is measured by the pressure of the high-pressure reactor, which can be 3-50 atm, and the reaction time is 10-48 h.

[0014] Preferably, the wavelength of the illumination is in the range of 365-450 nm, the illumination intensity is 10-100 W, and the distance between the light source and the reactor window is 0.5 - 5 cm. For example, the illumination wavelength of the LED light source is generally 390 nm, and the power of the light source is 100 W. Other light sources may be xenon lamps, sunlight, etc.

[0015] Preferably, the reaction temperature is 25-90°C.

[0016] After the method of the present invention continuously photocatalytically oxidizes methane for 5 times, its output efficiency is still maintained at more than 90% of the highest output efficiency; the method of the present invention has a short process flow, low preparation cost, and does not require complex reaction equipment, which is conducive to practical application and has good industrialization prospects.

[0017] The preparation method of the heterogeneous plasmon photocatalyst based on P orbital metal provided by the present invention and the activation conversion reaction of saturated alkanes such as methane, ethane, propane, butane, etc. catalyzed by the photocatalyst have important scientific significance and application value for the conversion and utilization of greenhouse gases such as methane. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the prepared catalyst;

[0019] Figure 2 is the SEM morphology of the catalyst;

[0020] Figure 3 is the XRD spectrum of the catalyst;

[0021] Figure 4 This is the H NMR spectrum of the heterogeneous plasmon photocatalyst catalyzing the activation of methane into acetic acid;

[0022] Figure 5 This is the nuclear magnetic resonance hydrogen spectrum of Example 7 using nuclear magnetic resonance to analyze the reaction system. DETAILED DESCRIPTION

[0023] Embodiment 1:

[0024] 8 g of glucose was dissolved in 60 mL of water, and 5 g of antimony trichloride was added. The solution was evenly dispersed by ultrasonication and transferred to a stainless steel reactor with a polytetrafluoroethylene liner. The reaction was carried out at 200 °C for 24 h. The hydrothermal reaction system was taken out, separated by centrifugation, washed with water several times and then washed with ethanol to remove the unreacted solid raw materials. The reaction was carried out in a vacuum drying oven at 60 °C for 12 h and dried to obtain a catalyst precursor powder. The above product was heated to 5 °C min under an argon atmosphere. -1 The temperature was raised to 900 °C and calcined for 2 h to obtain the target plasmon photocatalyst, that is, the carbon material loaded with metal Sb, such as Figure 1 The SEM morphology of the samples is shown in Figure 2 As shown, after X-ray diffraction (XRD) testing, the obtained XRD spectrum is as follows: Figure 3 shown.

[0025] Embodiment 2:

[0026] 10 mg of photocatalyst Sb@C (the photocatalyst Sb@C was prepared in Example 1) was dispersed in 8 mL of 30 wt% aqueous hydrogen peroxide solution, transferred to a high-pressure reactor, and 30 atm of methane was introduced. The reactor was placed 5 mm from the light source and reacted at room temperature for 48 h under 100 W, 390 nm LED illumination. 3-Trimethylsilyl-1-propanesulfonic acid sodium (DSS) was used as an NMR internal standard, and the reaction system was confirmed by NMR to have acetic acid as the product, with a concentration of 3.66 mol / L.

[0027] Embodiment 3:

[0028] 10 mg of photocatalyst Sb@C (the photocatalyst Sb@C was prepared in Example 1) was dispersed in 8 mL of 30 wt% aqueous hydrogen peroxide solution, transferred to a high-pressure reactor, and 40 atm of ethane was introduced. The reactor was placed 5 mm from the light source and reacted at room temperature for 48 h under 100 W, 390 nm LED illumination. Sodium 3-trimethylsilyl-1-propanesulfonate (DSS) was used as an NMR internal standard, and the reaction system was confirmed by NMR to produce acetic acid, with a concentration of 1.20 mol / L.

[0029] The target product is analyzed by nuclear magnetic resonance to obtain a hydrogen nuclear magnetic resonance spectrum, such as Figure 4 shown.

[0030] Embodiment 4:

[0031] 8 mL of 30 wt% aqueous hydrogen peroxide solution was added to the autoclave, 40 atm ethane was introduced, the autoclave was placed 5 mm from the light source, and the reaction was carried out at room temperature for 48 h under 100 W, 390 nm LED illumination. 3-Trimethylsilyl-1-propanesulfonic acid sodium (DSS) was used as the NMR internal standard, and the reaction system was confirmed by NMR to show that no product acetic acid was generated.

[0032] The reaction system was analyzed by nuclear magnetic resonance to obtain a hydrogen nuclear magnetic resonance spectrum, such as Figure 5 shown.

[0033] The concentration of acetic acid product can reflect the effect of the method. The provided NMR spectrum proves that there is only acetic acid product, which proves that the reaction has excellent selectivity. The method can prepare high-concentration acetic acid under photocatalysis, which proves that the method has excellent effect and efficiency in the application of activation and conversion of gaseous alkanes.

Claims

1. A method for preparing a heterogeneous plasmon photocatalyst based on p-orbital metal, characterized in that: The heterogeneous plasmon photocatalyst is prepared using p-orbital metal compounds and carbon sources as raw materials. The prepared plasmon photocatalyst can be used to achieve the catalytic activation conversion reaction of gaseous saturated alkanes: ； Among them, C(sp 3 )—H is a gaseous saturated alkane, for example, the gaseous saturated alkane is methane, ethane, propane or butane.

2. The method according to claim 1, characterized in that: The preparation method of the heterogeneous photocatalyst comprises: dispersing a p-orbital metal compound in a protic solvent, adding a carbon source, reacting at 120-300°C for 4-36 hours to obtain a preliminary product; and drying the preliminary product and calcining it in an inert gas atmosphere to obtain a final catalyst.

3. The method according to claim 2, characterized in that: The p-orbital metal compound is one, two, three, four, five or six of the compounds of Sn, Sb, In, Pb, Bi and Ga, and the compound is a metal halide, a nitrate compound or an oxide, such as the p-orbital metal compound is tin tetrachloride, bismuth trichloride and / or antimony trichloride, and the concentration of the p-orbital metal compound is 0.01-1.0 mmol / mL based on the volume of the protic solvent.

4. The method according to claim 2, characterized in that: The carbon source is one or more of glucose, cellulose and starch, and the molar concentration of the carbon source is 0.01-1.0 mmol / mL based on the volume of the protic solvent.

5. The method according to claim 2, characterized in that: The protic solvent is one or more of water, methanol, ethanol and ethylene glycol.

6. The method according to claim 2, characterized in that The drying conditions of the preliminary product are 50-80°C for 8-24 h.

7. The method according to claim 2, characterized in that The calcination temperature is 600-1000°C, the calcination time is 2-6h, and the atmosphere is inert.

8. The catalyst prepared by the method according to any one of claims 1 to 7, characterized in that: The catalyst is a carbon material-supported metal catalyst.

9. The method for converting saturated alkanes into acetic acid using a catalyst as claimed in claim 8, characterized in that: Gaseous saturated alkanes are catalyzed by plasmon photocatalysts and reacted in a stainless steel reactor in the presence of an oxidant and water under light irradiation at room temperature for 24-60 hours to obtain a final product; the amount of the plasmon photocatalyst is 0.05-2.0 mg / mL; the amount of the gaseous saturated alkanes is measured by the pressure of the reactor, and its amount can be 1-50 atm; the amount of the oxidant aqueous solution can be 5-10 mL, and the oxidant concentration is 1-30 wt%; preferably, the oxidant is an aqueous hydrogen peroxide solution.

10. The use according to claim 9, characterized in that: The wavelength of the light is in the range of 365-450 nm, the light intensity is 10-100 W, and the distance between the light source and the reactor window is 0.5-5 cm.

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